1. Field of the Invention
The present invention relates to a measuring device for measuring the angle of rotation of a machine shaft between a reference angular position of the shaft and the angular position at the instant of the occurrence of a phenomenon caused by the operation of the machine. The device includes transducers which transmit a number of pulses when the shaft passes the reference angular position and the machine-typical phenomenon occurs, the pulses being feedable to a processing circuit which generates an angle proportional signal out of the time interval between the passing of the shaft at the reference angular position and the occurence of the machine-typical phenomenon whereby said transducer signals a feedable to a threshold value switch, preferably to a comparator.
2. Description of the Prior Art
The principle of such a measurement mentioned above is to produce a gate signal with a duration equal to the duration while the rotation of the shaft is to be measured. For the specification of the angle in degrees of angle it is necessary to transform the duration of the gate signal into degrees of angle. To produce the gate signal it is necessary that with the aid of transducers at the beginning and the end of the gate signal a pulse or an edge of the pulse is obtained at each cycle of rotation. If such an angle measurement takes place at an internal combustion engine, it may happen that the beginning and the end of the gate signal cannot be defined by a single transducer pulse but only by the first pulse of a group of pulses which is cyclically repeated. A known method to fade out pulses which follow the first one is to start a monostable sweep circuit with the first pulse, whereby the running time of the sweep circuit is larger than the duration of the emission of the group of pulses. If the amplitude of the first pulse is substantially higher than the following pulses of the group of pulses it is possible, as known from German Offenlegungshrift No. 2 246 252, to avoid a multiple triggering with a simple threshold value switch. But if some of the pulses of the group have equal amplitudes and the length of the periodical groups of pulses is not short in respect to the period, using the method disclosed by the above mentioned specification avoidance of multiple triggering operation in cases of a greater engine speed range is only possible if the running time of the monostable sweep circuit is changeable in accordance with the engine speed. At a broad speed range therefore repeated changing of the running time of the monostable sweep circuit may be necessary and thus the required resources have to be significantly higher.